swift - 为什么 Swift 不接受这个 NSCalendar 方法调用？

Question

let dateComponents = NSCalendar.currentCalendar().components(.MonthCalendarUnit, fromDate: dateCreated, toDate: NSDate(), options: 0)

我试图在几个月内找出两个 NSDate 之间的区别，但此功能不合作。它一直提示“调用中有额外的参数‘toDate’”，但它肯定应该存在。

Answer 1

extension NSDate {
    func monthsFrom(date:NSDate) -> Int{
        return NSCalendar.currentCalendar().components(.CalendarUnitMonth, fromDate: date, toDate: self, options: nil).month
    }
}

let dateX = NSCalendar.currentCalendar().dateWithEra(1, year: 2014, month: 11, day: 28, hour: 5, minute: 9, second: 0, nanosecond: 0)!
let dateY = NSCalendar.currentCalendar().dateWithEra(1, year: 2015, month: 1, day: 1, hour: 22, minute: 51, second: 0, nanosecond: 0)!

let months = dateY.monthsFrom(dateX)  // 1